This invention relates, in general, to an apparatus for tape automated bonding (TAB), including, but not limited to an apparatus for distributing a nonoxidizing gas and removing ambient air from a bonding area.
TAB is usually done by gang bonding of a plurality of leads attached to a tape to bumps on a semiconductor chip. This is done utilizing a means to apply heat and pressure to the plurality of leads of the tape and the bumps on the chip. The plurality of leads are typically tin plated and the bump is typically gold. A gold-tin eutectic bond is formed between the lead and the bump.
Although TAB bonding is very reliable, some TAB bonded devices still experience lead lifts, and nodules, and bump lifts. Lead lifts are due to inadequate lead to bump eutectic bonds. Nodules are extruded tin-gold lumps which could cause shorts between the the plurality of leads and the bump to the surface of the semiconductor chip, which are caused by insufficient melting or wetting of the tin causing insufficient wetting of the eutectic. Better wetting also will result in better adhesion which creates a more robust bond. Cracks formed in the metal interface between the bump and the semiconductor chip cause the bump to lift after temperature cycling or high temperature storage or other tests. Thus, it is desirable to improve the TAB bonding process to reduce or eliminate the lead lifts, nodules, and bump lifts.